docs: def is_relation_made(relation, keys='private-address'):
      '''
      Determine whether a relation is established by checking for
      presence of key(s).  If a list of keys is provided, they
      must all be present for the relation to be identified as made
      '''
      if isinstance(keys, str):
          keys = [keys]
      for r_id in relation_ids(relation):
          for unit in related_units(r_id):
              context = {}
              for k in keys:
                  context[k] = relation_get(k, rid=r_id,
                                            unit=unit)
              if None not in context.values():
                  return True
      return False